Biopsy accuracy

[Guest guest]

As good as our current indicators (PSA, biopsies) of early prostate cancer may be, they are far from perfect.

Consider the challenge of a needle biopsy. One inserts hollow probes the size of a fat sewing needle into a prostate, which can vary in size from a walnut to perhaps twice as large. The standard used to be 6 or 8 cores; today 10 to 12 are 'standard'. So, for early prostate cancers in the PSA era, how accurate are the results of a biopsy?

The following presentation discussed this issue for typical first biopsies indicating 'low risk' prostate cancer-- PSA less than 10, Gleason sum 6, 3 or less positive cores, less than 50% of any core involved. In today's era of PSA screening, this is perhaps typical of positive results for a first biopsy performed because of a PSA in the range of 3 to 5.

297 men diagnosed with 'low risk' cancer were re-biopsied 6 months later with at least 10 cores.

For 97 of these men, about one-third, the second biopsy found NO sign of cancer. So, does this mean the small cancers found in the first biopsy disappeared in 6 months? Not likely. More probably this is an indication of the inherent sampling inaccuracy of current biopsies-- the small cancers found in the first biopsy were simply missed by the needles in the second biopsy. So, can one assume the inverse-- that a third of initial biopsies may miss a small cancer? Perhaps. However, a missed small Gleason 3+3 cancer is very likely to be slow growing, so followup tests-- PSA, DRE's, perhaps the new PCA3 urine test-- would be appropriate for one who had a biopsy triggered by reasons to suspect cancer, but the initial biopsy was negative.

For the 200 men with positive second biopsies, a total of 30% were upgraded or upstaged (second biopsy showed higher Gleason sums. or more positive cores or more core involvement). Does this mean that their cancers progressed in that 6 months? Not likely. More probably this again is an indication of the inherent sampling inaccuracy of a needle biopsy and the second biopsy sampled higher-stage tumors than the first.

So where does this leave one in considering the results of a biopsy, whether positive or negative?

The lesson seems to be that one needs to recognized that no diagnostic is perfect, and look at all the available indi>

For the 200 men with positive second biopsies, a total of 30% were upgraded or upstaged (second biopsy showed higher Gleason sums. or more positive cores or more core involvement). Does this mean that their cancers progressed in that 6 months? Not likely. More probably this again is an indication of the inherent sampling inaccuracy of a needle biopsy and the second biopsy sampled higher-stage tumors than the first.

So where does this leave one in considering the results of a biopsy, whether positive or negative?

The lesson seems to be that one needs to recognized that no diagnostic is perfect, and look at all the available indicators in assessing one's true situation. If the initial, or even a repeat, biopsy was negative, continued PSA monitoring and DRE's seems appropriate. If the first or second biopsy is positive but meets the "low risk" criteria, then it seems appropriate to base treatment decisions not just on the biopsy results but also one's PSA and DRE history. And of course, it is always advisable to have a second opinion on the pathology of the biopsy cores.

Clearly we need better biomarkers, imaging, and genetic tests to support how best to treat prostate cancer!

The Best to You and Yours!

Jon in Nevada

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AUA 2010 - The rate of upgrading and upstaging on immediate repeat biopsy in patients eligible for active surveillance is not related to extent of first biopsy - Session Highlights

Presented by S. Yee, Ari Adamy, Rodrigo Pinochet, andra C. Maschino, Angel M. Cronin, Bertrand Guillonneau, T. Scardino, and Eastham at the American Urological Association (AUA) Annual Meeting - May 29 - June 3, 2010 - Moscone Center, San Francisco, CA USA

Written by P. , MD

Monday, 31 May 2010

SAN FRANCISCO, CA USA (UroToday.com) - Patients entering active surveillance (AS) protocols will have PSA doubling time determined and repeat prostate biopsies performed longitudinally to monitor the prostate cancer (CaP) for signs of progression and need for intervention. In fact, some centers will repeat a second prostate biopsy a short time after the initial one to better minimize the possibility for undergrading or understaging. Dr. Yee and colleagues at Memorial Sloan-Kettering Cancer Center evaluated of the initial biopsy and whether the re-biopsy confirmed that these patients were candidates for AS. Between 1993 and 2009, 531 patients were identified as potential candidates for AS.

All patients had a PSA<10ng/ml, Gleason score =6, cT2a or less, <3 positive cores and =50% of cores involved by tumor. 297 patients had an immediate second biopsy (within 6 months of initial biopsy) with at least 10 cores taken. Cases were considered upgraded or upstaged if they no longer met inclusion criteria based on the result of the re-biopsy. The extent of initial biopsy was categorized as adequate (= 10 cores) or inadequate (<10 cores). The association between initial biopsy extent and results of re-biopsy was tested using Fisher's exact test.

For the 297 re-biopsied within 6 months, the median time to re-biopsy was 3.5 months. The median PSA at diagnosis was 4.3 ng/ml.

One-third of patients (97 men) had no evidence of cancer on the repeat biopsy. Of the 200 (67%) men with cancer on repeat biopsy, 64 (32%) had a Gleason score 7 or more, 55 (28%) patients had more than 3 positive cores, and 28 (14%) had more than 50% of a core involved by tumor.

A total of 90 (30%) patients were upstaged or upgraded.

There was no significant difference in upstaging or upgrading between those with an adequate or inadequate initial biopsy.